Bimodal polymers produced using two or more different catalyst types—bimetallic catalysts—are of increasing interest, especially in producing polyethylene and other polyolefins. See, for example, U.S. Pat. No. 5,525,678. However, problems exist in using these bimetallic catalysts, especially in the gas phase. One problem is catalyst activity, which should be as high as possible in order to economize the process, as catalysts costs are significant.
One method of improving catalyst efficiency in gas phase processes is to improve upon the catalyst used in the process. A promising class of single-site catalysts for commercial use includes those wherein the metal center has at least one extractable fluorine (or fluorine “leaving group”). Disclosures of such catalysts include U.S. Pat. No. 20020032287; U.S. Pat. No. 6,303,718; U.S. Pat. No. 6,291,615; U.S. Pat. No. 4,874,880; U.S. Pat. No. 3,896,179; WO 97/07141; DE 43 32 009 A1; EP-A2 0 200 351; EP-A1 0 705 849; E. F. Murphy, et al., Synthesis and spectroscopic characterization of a series of substituted cyclopentadienyl Group 4 fluorides; crystal structure of the acetylacetonato complex [(acac)2(η5-C5Me5)Zr(μ-F)SnMe3Cl], DALTON, 1983 (1996); A. Herzog, et al., Reactions of (η5-C5Me5)ZrF3, (η5-C5Me4Et)ZrF3, (η5-C5M45)2ZrF2, (η5-C5Me5)HfF3, and (η5-C5Me5)TaF4 with AlMe3, Structure of the First Hafnium-Aluminum-Carbon Cluster, 15 ORGANOMETALLICS 909-917 (1996); F. Garbassi, et al., JOURNAL OF MOLECULAR CATALYSIS A: CHEMICAL 101 199-209 (1995); and W. Kaminsky, et al., Fluorinated Half-Sandwich Complexes as Catalysts in Syndiospecific Styrene Polymerization, 30(25) MACROMOLECULES 7647-7650 (1997). Use of such single site catalyst components in a olefin polymerization system is desirable, especially in gas-phase polyethylene polymerization. However, it is often not commercially practical to produce such fluorided metallocene catalysts.
Methods of fluoriding metallocene catalyst components are disclosed by Z. Xie et al., Synthesis, Molecular Structure, and Reactivity of Organolanthanide Fluoride Complexes, [{(Me3Si)2C5H3}2Ln(μ-F)]2 (Ln=La, Nd, Sm, Gd) and [(C5H5)2Ln(μ-F)(THF)]2 (Ln=Y, Yb), 17 ORGANOMETALLICS 3937-3944 (1998); E. F. Murphy et al. in Organometallic Fluorides: Compounds Containing Carbon—Metal—Fluorine Fragments of d-Block Metals, 97 CHEM. REV. 3425-3468 (1997); W. W. Lukens, Jr. et al. in A π-Donor Spectrochemical Series for X in (Me5C5)2TiX, and β-Agostic Interactions in X=Et and N(Me)Ph, 118 J. AM. CHEM. SOC. 1729-1728 (1996); and P. M. Druce et al. in Metallocene Halides: Part I. Synthesis, Spectra, and Redistribution Equilibria of Di-π-cyclopentadienyl-Ti(IV), —Zr(IV), and —Hf(IV), 14 J. CHEM. SOC. 2106-2110 (1969). However, these methods fall short of a desirable, cost effect commercial method of making fluorided metallocene catalyst components. It would be desirable to improve the method of producing fluorided metallocenes, as well as its us in bimodal polymerization processes, especially for bimodal gas phase polymerization processes. The present invention is directed towards solving this and other problems.